5th firing of sasukenei kiln

[Jesse]

I'd like to share some of the results of my latest firing. Loading
strategy was a little different than my last firing, a result of
having more small pieces. Also, I had more help with the load and
firing, which I'd done largely by myself up to now. I guess I'm
confident enough to risk others' work now. We fired for 38 hrs to
c12-10, 2390f by the pryrometer. My work went in green and unglazed,
though my helpers brought bisqueware, some of which had glazes. The
large quantities of ash that characterize this kiln were present once
again, and the kiln seemed really easy to fire and raise temp- very
responsive. No smoke above 500f. The unloading did reveal one
unfortunate detail. I used a lot of shells for my side-fired pieces,
and while I've had luck with them in other kilns, for some reason they
fluxed out in this kiln, fusing the clay with the wadding I filled the
shells with. Particularly in the front. I would have been much
better off just going with wadding or quartz stones. Maybe it's the
amount of vapor this kiln produces, or the intense heat, whichever, it
did mean I had a much higher loss rate for this firing. ouch. Still,
there were enough nice pots and a few racers to make the firing a
successful one. Plus I introduced woodfiring to a couple
inexperienced guys who seemed to really take to the process and were
excited by the results. The pics are at:
flickr.com/photos/41125745@N00/
enjoy,
Jesse in Maine

[Lee]

Looks like a great firing Jesse! Can you point us to photos of the
kiln? What kind of wood did you use?

Thanks,
--
Lee Love in Minneapolis
http://mingeisota.blogspot.com/
"The intuitive mind is a sacred gift and the rational mind is a
faithful servant. We have created a society that honors the servant
and has forgotten the gift." -- Albert Einstein

[CRAIG]

Jesse: Yes indeed a good firing. Why do you think the shells didn't work. This is the first time I've ever heard of that, but with wood firing it's always something.
Make Good Pots
~Craig
New London MN
http://woodfiredpottery.blogspot.com/

--
Photo log at:  http://claycraft.blogspot.com/
To unsubscribe send email to Claycraft-...@googlegroups.com

[Lee]

Jesse,

High temp doesn't trouble shells. Shimaoka's firechamber
and yohen chamber were very hot, plus cone 13. What did you use for
wadding in the shells? He used a fireclay/alumina mixture.

[Hank Murrow]

On Nov 27, 2009, at 4:37 AM, Jesse wrote:

> The unloading did reveal one unfortunate detail. I used a lot of
> shells for my side-fired pieces,
> and while I've had luck with them in other kilns, for some reason they
> fluxed out in this kiln, fusing the clay with the wadding I filled the
> shells with.

Jesse;

Try soaking the offending pots in water for a day or so. I'm betting
the shells will dissolve so they can be brushed off. I use a weldors'
stainless steel brush for this.

Cheers, Hank

[Lee]

Soaking doesn't take long. But be careful with the mush, it is caustic.

[Ann Brink]

Some of you seem to have been able to view these pots on Flickr. When I
click on the link I just get the address in an email window-very
frustrating!
Ann

> --
> Photo log at: http://claycraft.blogspot.com/
> To unsubscribe send email to Claycraft-...@googlegroups.com

--------------------------------------------------------------------------------



No virus found in this incoming message.
Checked by AVG - www.avg.com
Version: 9.0.709 / Virus Database: 270.14.83/2529 - Release Date: 11/26/09
11:42:00

[Lee]

http://flickr.com/photos/41125745@N00/

Maybe this will work?   If not, try cut and paste.

[Ann Brink]

That is working-Thanks, Lee.

Ann

--
Photo log at: http://claycraft.blogspot.com/
To unsubscribe send email to Claycraft-...@googlegroups.com

No virus found in this incoming message.
Checked by AVG - www.avg.com

Version: 9.0.709 / Virus Database: 270.14.84/2530 - Release Date: 11/26/09 23:58:00

[Neon-Cat]

Nicest and most interesting thing I've seen in days, Jesse! Good presentation, too -- it imparts the total ambiance of your pottery. I can almost hear residuals of the kiln firing in the pots and smell a remnant of lingering light smoke scent. And gee, that ham looked real tasty!   Dumb question (no wood firing experience) -- is kiln atmosphere so violent it takes away edges and lips? Were those small cups in the first photo ragged before firing or just after? The effect is nice, I'm just curious.  Thanks for sharing!   Marian

[Lee]

Shots of Jesse's kiln:

http://www.flickr.com/photos/41125745@N00/3186770633/in/set-72157594447981007/

http://www.flickr.com/photos/41125745@N00/3457679770/in/set-72157594447981007/

[Louis Katz]

Nice looking pots

Without seeing the stuck wads it is hard to come up with a reason. 

Calcium Carbonate heated above around 1500 F becomes calcium Oxide or quick lime

in contact with water or water vapor it becomes calcium hydroxide aka slaked lime. Hard burnt calcium oxide or impure calcium oxide can be much slower to slake into calcium hydroxide. You might have to soak or a while. It also expands as it slakes, this is what causes lime blows to blow.

It seems and I am not sure of this, that sometimes the shells have enough salt in them to cause troubles. This seems to happen when I collect dry shells on the beach near my house. I think this is the result of lots of salt water being splashed on them and then drying.

Slaked lime can be used as white wash, and as a mortar for brick, mix it with sand and stack your wall, over a period of years your calcium hydroxide turns into calcium carbonate and you end up with sandy limestone.

It is a strong enough flocculant that it creates troubles in glazes.

Louis

Lee, thats a great Einstein quote.

[Jesse]

Thanks folks, the shell thing confuses me too- the spots where they
were in contact with the pots was actually etched away in some cases,
shell gone, and the wad beneath the shell fused with the clay of the
pot. Pisser. Wadding is 50/50 hawthorne bond and silica sand. I
didn't have that problem with the pots in the back of the kiln, there
the shell just left the marks and halo I'm used to. But I had a
similar problem a few firings back, and attributed it to the shells.
These are different ones, but same dang problemo. Lee, I burnt w.
pine, cottonwood, ash, mixed hardwood- whatever I gleaned from the
roadside and lumber mill. Marion- those cups were handbuilt the way
you see them out of some rough textured slabs-something new.
js

[Lee]

On Fri, Nov 27, 2009 at 3:47 PM, Jesse <stes...@hotmail.com> wrote:
>
> Thanks folks, the shell thing confuses me too- the spots where they
> were in contact with the pots was actually etched away in some cases,
> shell gone, and the wad beneath the shell fused with the clay of the
> pot.  Pisser.  Wadding is 50/50 hawthorne bond and silica sand.

Jesse, maybe the wadding is the problem. Clay + silica +
whiting (the shell is calcium carbonate) is a standard mixture for a
good glaze. Shimaoka used a mixture of a high alumina clay and
alumina hydrate. I used EPK/Alumina 50/50, but you could even use
more Alumina, maybe 25 EPK and 75% Alumina hydrate.

> didn't have that problem with the pots in the back of the kiln, there
> the shell just left the marks and halo I'm used to.  But I had a
> similar problem a few firings back, and attributed it to the shells.

Is there is much heat and ash in the back? Woodash is impure whiting.

> These are different ones, but same dang problemo.  Lee, I burnt w.
> pine, cottonwood, ash, mixed hardwood- whatever I gleaned from the
> roadside and lumber mill.  Marion- those cups were handbuilt the way
> you see them out of some rough textured slabs-something new.
>

Does the green come from the pine and cottonwood? They use pine in
Japan for the green ash, but we didn't use it in the ash glaze
because of the iron content.

[Mike]

Jesse,
This thing with the shells happens to me too on occasion if the shells
were thin and or had a crack. Then they turn a sort of yellowish brown
color and seem to be melted, but they're usually not, at least
completely that is. Let the moisture get at them for a few days, and
don't knock the wads off, you might lose a chunk of your pot. After
you've given the shells some time to 'soften' (this may or may not
work), take a steel punch, the kind that are round and taper to a point,
and start pecking at that wad like a woodpecker. This will slowly wear
away the wad down to the shell. Keep pecking until the wad is gone, then
go over it with wet sandpaper. Usually this works, and doesn't take as
long as you would think. Sometimes after the wad is gone, it is easier
to get parts of unmelted shell out of there.

Mike
in Taku, Japan

karatsupots.com
karatsupots.blogspot.com
karatsupots-workshop.blogspot.com/



Jesse ????????:

[rickma...@comcast.net]

Jesse,
I have seen this before it is not a big deal except where the wad is welded to the pot.
I like to include some organic material (bran for example) into the wadding so that it is easier to grind.  (In the distant past soft brick had ground walnut shells to create the voids that help with the insulation properties of those bricks.)
It could be that your kiln is much hotter on the fire face next to the firebox that it has been in the past.
Mike's suggestion below is a good one, remember that gentle tapping with the center punch is a good tactic.
One other thing with organic material in the wadding it will begin to stink as the organic material rots.


YMMV,
Rick

----- Original Message -----
From: "Mike" <mi...@karatsupots.com>
To: clay...@googlegroups.com
Sent: Friday, November 27, 2009 1:59:34 PM GMT -08:00 US/Canada Pacific
Subject: Re: *ClayCraft* 5th firing of sasukenei kiln

[Louis Katz]

The slaked lime (formerly a shell) when thin hardens quickly with air.
As soon as you have removed the wad you should clean it. If it sits
for a few days it can be much more difficult.

Louis

[gary navarre]

I'm impressed too Jesse,

... and I got lost inside a couple links and ended up at the site of Masakazu Kusakabe whom I guess you designed the kiln from. Such a tall stack must have a hell of a draft and yet you got some good ash buildup.

With the shells, besides maybe being too thin (I didn't know that possibility yet) and salt absorption, I'd bet the silica in the mix is part of the problem. Lee and others have mentioned a more refractory mix of fire clay/kaolin would be better and I used my fire clay/kaolin/fine grog lag mix and added more alumina hydrate and kaolin. Haven't added sawdust yet so that's a thing to try too. I ran out of enough fine hard brick grog and broke into another bag I got from the brick yard that is white and quite mixed in grit. This is the first I've seen white grog and my brick guy never heard of grog so you can guess what went on when he placed the order. I got a bag of tan and one white. I sieved some fine out for body tests and course for wadding. Has ya ever heard of or used white grog and what is it made from?

The shot of green ware from different shelves is interesting and I've yet to leave much of anything unglazed in my first load yet but we are getting near making pots for the front near the firebox so I think that is where most folks set pieces for ash buildup eh, in the throat arch and even inside corners of the Bourry ash pit. I could see myself pulling pots out through the pignose but I would need a six foot hook. Someone suggested I make a "secret spot" but I really don't know where that is supposed to be so I'll just wing it. Seems I had the same problem with my prom date but this is not the kind of meeting to discuss juvenile 13Th. step disasters.

Let us see what happens with the shell suggestions through cleaning and be careful with the steel pick. Say, how often do you fire now so we can get an idea when to expect a new batch and if the ideas worked. At my pace it could be another six months before I light up and keep it lit so till then I guess we'll just stay in there eh!

Gary Navarre
Navarre Pottery
Navarre Enterprises
Norway, Michigan, USA
http://www.youtube.com/GindaUP
http://public.fotki.com/GindaUP/

--- On Fri, 11/27/09, Jesse <stes...@hotmail.com> wrote:

[Des & Jan Howard]

Gary
Around here the tan grog would be crushed hard fired
siliceous firebrick & the white grog would be hard
fired kaolin aka Molochite. We also have a pale cream
naturally hard fired grog, fireclay seat earth seam
that cooked up when the coal deposit above burned
millenia ago. BUT, I would get a sample of both of
yours to someone for test firing.
Des

gary navarre wrote:
> This is the first I've seen white grog and my brick guy
> never heard of grog so you can guess what went on when
> he placed the order. I got a bag of tan and one white.
> I sieved some fine out for body tests and course for
> wadding. Has ya ever heard of or used white grog
> and what is it made from?

--
Des & Jan Howard
Lue Pottery
Lue NSW
Australia
2850

02 6373 6419
www.luepottery.hwy.com.au
-32.656072 149.840624